This invention relates to a connection structure for connecting a wire and a terminal with each other by ultrasonic vibration.
Japanese Patent Application Publication No. H7-70345 has disclosed a structure in which a covering portion of a covered wire is melted and removed by applying ultrasonic vibration so as to conductively connect cores of the covered wire to a terminal.
In a conventional connector as shown in FIGS. 1A, 1B and 2, first member 1 and second member 2 formed of resin oppose each other.
On a top face of the first member 1 are formed groove portions 3 and small concave portions 4. A terminal 5 is inserted in the groove portion 3 of the first member 1. On the terminal 5 is placed a covered wire 6. The covered wire 6 is placed on the terminal 5 in such a condition that a plurality of its cores are covered with a covering portion made of resin.
On a bottom face are formed protrusions 7 engaging with each of the groove portions 3 of the first member 1 and small convex portions 8 fitting into each of the concave portions 4 of the groove portions 3.
As shown in FIG. 2, the terminal 5 and covered wire 6 are inserted into the groove portion 3 of the first member 1 and then the protrusions 7 of the second member 2 are engaged with the groove portions 3 of the first member 1. As a result, the terminal 5 and covered wire 6 are pressed by the second member 2 and first member 1. At this time, the terminal 5 and covered wire 6 are partly bent at the engagement portions between the concave portion 4 and the convex portion 8, thereby preventing slippage thereof.
Then, with the terminal 5 and the covered wire 6 being pinched by the first member 1 and the second member 2, ultrasonic vibration is applied using a horn while a pressure is being applied thereto. By heat generated during the ultrasonic vibration, the covering portion of the covered wire 6 is melted and removed, so that the inside cores are exposed. Then, the exposed cores are conductively connected to the terminal 5. At the same time when this conductive connection is achieved, the first member 1 and the second member 2 are integrated so that a connector accommodating the terminals 5 and wires is produced.
FIG. 3 shows a structure for producing a multi-pole connector. On the first member 1 are formed a plurality of the groove portions 3. On the second member 2 are formed a plurality of protrusions 7 corresponding to the groove portions 3. After the terminal is accommodated in each of the groove portions 3, the covered wire is placed on each terminal. The covered wires are pinched by the first member 1 and second member 2, and by applying ultrasonic vibration while a pressure being also applied thereto, the connector is produced.
However, after the ultrasonic vibration is finished, the resin made first member 1 and second member 2 shrink due to a change of the temperature. Due to this shrinkage, contacting load making the terminal 5 and cores into contact with each other is reduced. Thus, there may be produced a contact failure between the terminal 5 and cores so that electrical connecting reliability may be reduced. Further, the terminal 5 and covered wire 6 are easy to be deviated when the connector is made or separated, so that a contact failure between the terminal 5 and cores likely occurs due to the deviation.